Conventional optical storage drives typically employ a single optical disk having a single recording surface for storing information. Use of a single disk allows the optical components, such as an optical beam source, mirrors, lenses and the head assembly, to be arranged relative to the recording surface in a manner that optimizes the size and cost of the drive. Although this results in a low-cost device having a relatively small form factor for, e.g., a 51/4-inch disk, the storage capacity of the drive is limited to that provided by a single surface.
To provide increased storage capacity, a storage device can include an array of disks having multiple recording surfaces for storing information. The optical components of the multi-disk device are arranged to direct an optical beam onto each recording disk surface. Specifically, the components must be precisely aligned within the space constraints provided by a conventional single-disk drive; compatibility with such a form factor requires that the disks of the array be closely-spaced. Further, the optical components must be manufacturable within the cost constraints of the conventional single-disk drive optical components.
Known multiple-disk, optical storage drives generally are not compatible with the small form factor standard One example of such a drive involves a single head assembly mounted on an elevator carriage. The head assembly is relatively large and heavy because it includes a complete optics system that physically moves within the drive to bring the optical beam to each recording disk surface. The massive head assembly causes ringing during positioning of the head between disk surfaces. This, in turn, causes an increase in the access time of the drive because time is spent waiting for the ringing to cease. In addition, the performance of the system is degraded, particularly when the requested data is dispersed among multiple disk surfaces.
Another example of a multiple-disk storage drive involves a multiple head assembly system. Here, each recording surface has its own complete optics system, including optical beam source and detectors, mirrors and lenses, mounted to an associated head assembly. This type of system is costly because of the duplication of optical components. Although the system provides simultaneous accesses to the recording surfaces, duplication of the optical components results in a large size and mass.
Therefore, it is desirable to provide a high-performance, multiple-disk optical storage device that meets the size and cost constraints of conventional disk drives.
It is also desirable to provide a high-performance, multiple-disk storage device having an optical beam distribution system.
It is also desirable to provide an optical beam distribution system that enables use of a small objective lens for reducing the size and weight of an air bearing slider of an optical head assembly.